Re: [PATCH] mm: Fix access_remote_vm() regression on tagged addresses

[Linus Torvalds]

On Thu, 10 Aug 2023 at 05:42, Schimpe, Christina
<christina.schimpe@xxxxxxxxx> wrote:
>
> We don't have any LAM support in GDB yet, we are just working on it.
> We currently rely on that feature, but could still change it. We don't
> necessarily require /proc/PID/mem to support tagged addresses.
>
> ARM's TBI support in GDB does not rely on /proc/PID/mem to support tagged
> addresses AFAIK.

Ahh. That would explain why nobody noticed.

I do wonder if perhaps /proc/<pid>/mem should just match the real
addresses (ie the ones you would see in /proc/<pid>/maps).

The main reason GUP does the untagging is that obviously people will
pass in their own virtual addresses when doing direct-IO etc.

So /proc/<pid>/mem is a bit different.

That said, untagging does make some things easier, so I think it's
probably the right thing to do.

             Linus